Rocker Neil Young is boycotting coffee giant Starbucks over the company's involvement in an ingredient-labelling lawsuit in Vermont.

Lawmakers in the New England state passed a bill earlier this year (14) requiring all food products - with the exception of dairy, meat, and alcohol - containing genetically modified organisms (Gmos) to be labelled as such by 1 July, 2016.

Weeks after the law passed, four food industry organisations filed a lawsuit against the state challenging the constitutionality of the ruling, and among the plaintiffs is the Grocery Manufacturers Association, which Starbucks and sustainable agriculture company Monsanto are members of.

After discovering Starbucks bosses are involved with the lawsuit, the Heart of Gold hitmaker took to his website to tell his fans he is officially denouncing the company in support of Vermont's lawmakers.

He wrote, "I used to line up and get my latte everyday, but yesterday was my last one. Starbucks has teamed up with Monsanto to sue Vermont, and stop accurate food labeling."

"Monsanto might not care what we think - but as a public-facing company, Starbucks does. If we can generate enough attention, we can push Starbucks to withdraw its support for the lawsuit, and then pressure other companies to do the same."

He continued, "Considering that Starbucks has been progressive on Lgbt (Lesbian, Gay, Bisexual and Transgender) and labor issues in the past, it's disappointing that it is working with the biggest villain of them all, Monsanto.

"There's much more at stake here than just whether Gmo foods will be labeled in a single U.S. state. Vermont is the very first state in the U.S. to require labeling. Dozens of other states have said that they will follow this path - in order to encourage this, we need to ensure that Vermont's law stands strong."

Young also urged his fans to "pressure and call out members of the Grocery Manufacturers Association" by donating or signing a petition on, a movement against the growing power of large corporations.